tRNA

Decoding

subunits

Peptide-chain transfer

Another round of accurate decoding

b Mistake

a No mistake

tRNA

translocation

Premature termination

Figurc 1 Ribosomal matchmaking. a. Normally, Ihe correct tRNA (yellow) enters the A site ot the ribosome and the appropriate amino acid (red) is incorporated into the growing peptide chain, which transfers from tRNA in the P site to the tRNA at the A site. Both tRNAs, as well as the mRNA, then shift towards the E site. b, When mistakes are madę and the mismatched codon-anticodon helix (indicated by a red cross) translocates to the P site, the ribosomal complex becomes susceptible to premature termination by translation factors such as RF2, and the erroneous sequence is prematurely released.

From the following aiticle:

Protein synthesis: Errors rectified in retrospect

Kun Fredrick &. Michael lbba, Naturę 457,157-158(8 January 2009)